By a strange coincidence, there is just such a lack of electricity as I am writing, and the barometer has rapidly sunk to such a degree that a storm seems inevitable.
One of the chief difficulties in dealing with such a subject as this is to know where to begin. We will, however, do our best to take a general view of it, without going into details.
Many centuries ago it was well known that amber, if rubbed with a dry cloth, would first attract, and then repel, various small and light substances. Indeed, the Greek word for amber, namely, Elektron, has given its name to the modern science of Electricity. Many other substances, such as glass, sealing-wax, &c., possess the same property.
This frictional electricity is but transient, the electric fluid, if we may be allowed to use the term, being driven out by main force from the material in which it was latent, just as fire is procured by the friction of two dry sticks. There is, however, a form of Electricity called Galvanism, from its discoverer, Galvani, who, somewhere about 1790, discovered that the limbs of a dead frog might be excited to action by electricity applied to the nerves.
Afterwards, Volta of Pavia, from whom the Voltaic Pile is named, took up Galvani’s discoveries, and produced electricity without friction, by the contact of differently conducting substances.
The right-hand figure represents the Voltaic Pile. It is composed of a series of plates arranged in the following manner—Zinc, Silver, and Cloth, the whole being moistened with diluted acid. Copper will answer the purpose nearly as well as silver, and is not so costly. A very simple mode of demonstrating the presence of electricity is by taking a piece of zinc and a silver coin, and placing one below and the other above the tongue. If the two be then brought together, a very peculiar taste is perceived, and a sudden flash of light seems to pass across the eyes.
The illustration represents on the right hand the Voltaic Pile as at present made, and on the left are the two hind-legs of a frog, with the upper part of the nerves made bare for the purpose of experimenting. The dotted lines show the extent of the movements of the leg when the galvanic current is passed through the nerves.
Now we come to a plan whereby electricity can be accumulated, or locked up, so to speak, and be discharged at once with a definite shock instead of being poured away by degrees. This can be done in many ways, the most common being that which is known by the name of the Electric Jar. It is a glass vessel coated within and without with tin-foil, and having a metal rod passing through the cork in such a way that while the lower end is in contact with the inner coating of tin-foil, the other end is guarded by a ball.
Electricity is now poured into the interior of the jar, and, when contact is made between the inner and outer coatings, a sudden discharge takes place. If a number of persons hold each other’s hands, and those who form the two extremities touch the outer coating and the ball which communicates with the inner coating, a sharp discharge is at once made, passing through all the bodies, and inflicting a smart shock, especially at the elbows.